The key to successful semantic maps from students is allowing them to see how it should look as a finished product. Using a white board and multi-colored markers if possible, walk students through an example, making sure to include the core concept and at least three strands, each with at least two supports. Taking ideas from the class to include and making sure they are copying down the model will keep them engaged as you work through the example. If you don't want to "give them the answers" to the map you're hoping they will produce, use a previous unit or common experience to create the class map.
One way to assess understanding of the semantic map idea as well as the concept being taught is to have students work in pairs on a semantic map.
1. Give them the core concept and allow pairs two to three minutes to discuss what they know about it. This step can also be done as a class.
2. Allow about two minutes for each student to write down three strands.
3. Have students trade papers with their partners and give them three minutes to write at least two supports for each of their partner's strands.
4. GIve pairs five minutes to explain their supports to each other and discuss any others that might be useful.
5. Each member of the pair will work individually to create a map using the three best strands the pair produced.
To help young writers collect and organize their thoughts, have the class work together on a semantic map for a composition they will then write individually. Put the core concept on the board and go around the room, having each student contribute either a strand or support for an existing strand. Have students copy down the strands and support they will use for their compositions. Be sure to demonstrate how one of the strand/support clusters can be turned into part of a composition.
Semantic maps make an excellent vocabulary building exercise. As part of vocabulary exploration activities, have students use each word as the core concept of a map. Give them the following strands: part(s) of speech, synonyms, antonyms and connections to other vocabulary words, leaving them to fill in the required supports. Encourage them to think about additional strands to use for some of the words.